1. Field of the Invention
The present invention relates to a nickel electrode for an alkaline storage cell such as a nickel-hydrogen storage cell, a nickel-cadmium storage cell, a nickel-zinc storage cell and the like and a manufacturing method for the same. More particularly, the present invention relates to a nickel electrode made of a nickel hydroxide active material containing a conductive agent and a manufacturing method for the same.
2. Description of the Prior Art
In recent years, demands for a high performance storage cell have increased for use in rapid popularization of portable electronic and communication equipments. In the field of alkaline storage cells, there have been proposed various improvements for enhancing the utilization factor of a nickel hydroxide active material in a positive electrode of the alkaline storage cell. For example, there have been proposed a method for adding a cobalt compound or metal nickel powder to a nickel hydroxide active material as a conductive agent and a method for precipitating a cobalt compound or metal nickel powder on the surface of a nickel hydroxide active material.
Although the conductivity of a cobalt compound having an oxidation value of 2 is low, the cobalt compound becomes a higher order state when the oxidized at during initial charge and discharge of the cell. In addition, cobalt hydroxide is oxidized by charging of the cell and precipitated on the surface of the nickel hydroxide active material as oxy-cobalt hydroxide. When the cell is discharged, the oxy-cobalt hydroxide is partly reduced and dissolved in electrolyte. With such reaction of the cobalt hydroxide, a conductive network is uniformly formed on the surface of the nickel hydroxide active material. This is useful to reduce the electrical potential of an isolated portion and to enhance the utilization factor of the active material.
In the method of precipitating a cobalt compound on the surface of the nickel hydroxide active material, 1 discharge reaction of the active material occurs as represented by the following formula (1). EQU NiOOH+H.sub.2 O+e.sup.--.fwdarw.Ni(OH).sub.2 +OH.sup.-- (1)
The discharge reaction of the formula (1) is effected on the surfaces of nickel hydroxide particles in spherical form under the presence of a sufficient amount of H.sub.2 O and OH.sup.--. For this reason, if the amount of H.sub.2 O and OH.sup.-- is insufficient, the cobalt compound ineffective in the reaction of formula (1) is uniformly precipitated on the surfaces of the nickel hydroxide particles. This decreases the utilization factor of the active material.
On the other hand, if the conductive layer is irregularly formed on the nickel hydroxide particles, the utilization factor of the active material is enhanced by the reaction of formula (1), but it becomes difficult to uniformly form irregular conductive layers on the nickel hydroxide active material.